Electroacoustic transducer frame and method of making the same

Abstract

A frame of an electroacoustic transducer is made from a mixture of a thermoplastic resin and long fibers dispersed in the resin. The long fibers serve as reinforcing fibers. The long fibers have an average length sufficient to achieve a spring back effect. The spring back effect creases a foam structure. The electroacoustic transducer frame includes single-layer portions and three-layer portions. The single-layer portion is made of a non-foam layer. The three-layer portion is made of a pair of non-foam layers and a foam layer sandwiched by the non-foam layers. The electroacoustic transducer frame is lightweight, and has high internal loss, high rigidity and improved environmental resistance.

1. A molded frame for an electroacoustic transducer, the molded frame comprising a mixture of a thermoplastic resin and reinforcing fibers dispersed in the thermoplastic resin, the reinforcing fibers including long fibers, wherein an average length of the reinforcing fibers is at least 1 mm. 
     
     
       2. The molded frame according to  claim 1 , wherein rigidity of the reinforcing fibers is greater than rigidity of the thermoplastic resin. 
     
     
       3. The molded frame according to  claim 1 , wherein the thermoplastic resin is a crystal thermoplastic resin. 
     
     
       4. The molded frame according to  claim 1 , wherein the thermoplastic resin is an olefin resin including polypropyene. 
     
     
       5. A frame for an electroacoustic transducer, the frame comprising a mixture of a thermoplastic resin and reinforcing fibers dispersed in the thermoplastic resin, the reinforcing fibers including long fibers having an average length sufficient to achieve a spring back effect of the reinforcing fibers, the frame having single-layer portions and three-layer portions, each of the single-layer portions consisting of a non-foam layer, and each of the three-layer portions consisting of a pair of non-foam layers and a foam layer sandwiched by the pair of non-foam layers. 
     
     
       6. The frame according to  claim 5 , wherein the average length of the reinforcing fibers is at least 1 mm. 
     
     
       7. The frame according to  claim 5 , wherein rigidity of the reinforcing fibers is greater than rigidity of the thermoplastic resin. 
     
     
       8. The frame according to  claim 5 , thermoplastic resin is a crystal thermoplastic resin. 
     
     
       9. The frame according to  claim 5 , wherein the thermoplastic resin is an olefin resin including polypropylene. 
     
     
       10. The frame according to  claim 5 , wherein an average magnification of expansion upon foaming of the three-layer portion including the pair of non-foam layers is between about 1.1 and about 5.0 times. 
     
     
       11. The frame according to  claim 5 , wherein at least one of the single-layer portions has a through hole, in which a screw is received to permit attachment of the frame to an electroacoustic transducer. 
     
     
       12. The frame according to  claim 5 , wherein the electroacoustic transducer has a magnetic circuit in contact with at least one of the single-layer portions when the frame is attached to the electroacoustic transducer. 
     
     
       13. The frame according to  claim 5 , wherein the frame has a generally truncated conical shape and includes a front peripheral portion, a bottom portion and a plurality of bridges, and the plurality of bridges connect the front peripheral portion with the bottom portion at a plurality of the single-layer portions. 
     
     
       14. A method of manufacturing an electroacoustic transducer frame comprising the steps of:
 A) mixing and melting a thermoplastic resin with reinforcing fibers to obtain a molten resin-fiber mixture including the reinforcing fibers dispersed in the thermoplastic resin, the reinforcing fibers having an average length sufficient to achieve a spring back effect of the reinforcing fibers; and  
 B) injecting and filling the molten resin-fiber mixture into a cavity defined between two mold halves, and retracting at least one portion of the two mold halves such that the cavity is partly enlarged, to create an electroacoustic transducer frame having single-layer portions and three-layer portions, each of the single-layer portions consisting of a non-foam layer, and each of the three-layer portions consisting of a pair of non-foam layers and a foam layer sandwiched by the pair of non-foam layers.  
 
     
     
       15. The method according to  claim 14 , wherein the average length of the reinforcing fibers is at least 1 mm, and the reinforcing fibers are included in the resin-fiber mixture at about 5 to 80 weight % and the thermoplastic rein is included in the resin-fiber mixture at about 20 to 95 weight %. 
     
     
       16. The method according to  claim 14 , wherein rigidity of the reinforcing fibers is greater than rigidity of the thermoplastic resin. 
     
     
       17. The method according to  claim 14 , wherein an average magnification of expansion upon foaming of the three-layer portion including the pair of non-foam layers is between about 1.1 and about 5.0 times. 
     
     
       18. The method according to  claim 14 , wherein the thermoplastic resin is a crystal thermoplastic resin. 
     
     
       19. The method according to  claim 14 , wherein the thermoplastic resin is an olefin resin including polypropylene. 
     
     
       20. The molded frame according to  claim 1 , wherein the reinforcing fibers are included by 10-30% weight.